This invention relates generally to inkjet printers, and particularly, to a method and structure for wiping the printhead.
Inkjet printers use pens that shoot drops of ink onto media such as paper sheets. Each pen has a printhead formed with very small nozzles through which the ink drops are fired. The printhead is mounted on a bi-directionally movable carriage, such carriage being configured to reciprocate back and forth across the paper as printing occurs. The structure and operation of such printheads and carriages are well known to those skilled in the art.
In order to keep printheads in proper printing condition, most inkjet printers use a mechanism at some point along the printhead""s path to periodically service the printhead during normal use. Such mechanism generally includes a wiper that sweeps across the printhead to clear its printing surface of contaminants such as dried or drying ink.
A conventional wiper includes a chassis-mounted base and an elongate blade. The blade extends from the base to a tip that engages the printhead""s printing surface when the printhead passes across it. The blade is typically planar and is of a size determined by the physical characteristics of the printer in which it is used. The blade""s thickness is determined to produce a wiper that exerts a desired force on the printhead when the wiper is engaged with the printhead. Typically, the blade is made of flexible material.
FIGS. 1 and 2 illustrate a conventional wiper wiping a printhead. In FIG. 1, a cartridge 10 has an ink reservoir 12 and a printhead 14. The printhead 14 has a metal or plastic orifice plate 16 with two parallel columns of offset nozzles 18 formed on the plate 16. The orifice plate 16 is fixed to the surface of a semiconductor substrate (not shown).
FIG. 2 is taken along line Axe2x80x94A in FIG. 1 to illustrate an elastomeric wiper 20 wiping the printhead 14. As indicated, the wiper 20 is in the form of an elongate blade which includes a wiping region 22. The wiper 20, in particular the wiping region 22, presses against the nozzle plate 16 of the associated print cartridge to wipe off ink drops. During the wiping, however, the edge 22a of the wiping region 22 scratches exit regions 24 of the nozzles 18 as illustrated. Such scratches cause damages to the nozzles such that the exist regions 24 of the nozzles 18 are deformed. These damages affect the size, trajectory, and speed of ink drop ejection during printing, and in turn affect the inkjet printhead""s performance.
Accordingly, there is a need for a wiper that does not damages the nozzles"" exist regions.
In a preferred embodiment, the invention provides a wiper that does not scratch exit regions of nozzles during wiping process.
In a preferred embodiment according to the invention, a wiper for inkjet printhead has a slightly recessed wiping region at a first end. The recessed wiping region is positioned approximately opposite to columns of nozzles of the printhead during wiping and indirectly contacts the nozzles. Thus, the wiper does not directly contact the nozzles.
According to a further aspect of the invention, the wiper also has a non-recessed wiping region at the first end and adjacent to the recessed wiping region. The non-recessed wiping region presses against the printhead to exert desired forces for wiping. Preferably, the non-recessed wiping region maintains a gap between the printhead and the recessed wiping region.